AIDER MOI JEN PEUX PLUS!!!!!!!!!!!!!

Exercice 2 :

a) 1. D = (2 - 5x) (4x + 3) - (2 - 5x)²
D = 2 X 4x + 2 X 3 - 5x X 4x - 5x X 3 - [2² - 2 X 2 X 5x + (5x)²]
D = 8x + 6 - 20x² - 15x - (4 - 20x + 25x²)
D = 8x + 6 - 20x² - 15x - 4 + 20x - 25x²
D = - 45x² + 13x + 2

Pour x = - 1

D = - 45x² + 13x + 2
D = - 45 X (- 1)² + 13 X (- 1) + 2
D = - 45 X 1 - 13 + 2
D = - 45 - 13 + 2
D = - 56

b) 51² = 
(50 + 1)² = 
50² + 2 X 50 X 1 + 1² =
2 500 + 100 + 1 =
2 601

69² = 
(70 - 1)² = 
70² - 2 X 70 X 1 + 1² = 
4 900 - 140 + 1 = 
4 761

23 X 17 =
(20 + 3) (20 - 3) = 
20² - 3² = 
400 - 9 =
391

c) (x + 3)² = x² + 6x + 9
(2x - 5)² = 4x² - 20x + 25
(7x + 8) (7x - 8) = 49x² - 64